Development of advanced thermodynamic models for CO2 absorption: From numerical methods to process modelling

This thesis considers the development of predictive thermodynamic models for amine-based carbon capture processes, motivated by the imminent requirement for the reduction in anthropogenically produced carbon dioxide emissions. In the introduction, we show how the use of molecular-based equations of state, such as SAFT (Statistical Associating Fluid Theory), can be highly effective in this context. Due to the level of molecular detail captured in their theoretical development, one can reduce the reliance on experimental data by transferring their parameters based on sound physical arguments. In particular, the inherent chemical reactions in amine-based carbon dioxide absorption processes can be modelled by a physical association scheme, offering a vast simplification over the conventional treatments. In the following chapter a rate-based absorber model is presented to investigate the reactive capture of carbon dioxide CO2 using aqueous monoethanolamine (MEA) as a solvent. The SAFT-VR SW equation is used as the thermodynamic model. Due to the physical treatment of the reactions, the process model equations only needs to consider the apparent concentrations of the molecular species, while the reactions are implicit in the SAFT equation. With the assumption that the species diffuse as non-associated species, the rate of CO2 absorption is overpredicted, providing an upper bound on the solvent performance. A single parameter is adjusted to the pilot plant data, reflecting the reduction in mass transfer rate in the apparent CO2 in its aggregated form, which is found to be transferable over all of the pilot plant runs. The development of new models for the SAFT- Mie equation is then considered for improvement of the thermodynamic model. This is because the thermodynamic models developed for the SAFT-VR SW (used in the absorber) provide an inaccurate description of the liquid heat capacity and the heat of absorption of CO2. We consider a novel approach to the parameter estimation problem. It is shown that posing the ...